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20 April 2019, Volume 40 Issue 04

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Evaluations and Projections of Rice Yield from Multi-gridded Crop Model over China

SUN Qing, YANG Zai-qiang, YANG Shi-qiong, WANG Lin, ZHAO He-li, WEI Ting-ting, LI Jia-shuai, CHE Xiang-hong, ZHENG Xiao-hui

2019, 40(04):  199-213.  doi:10.3969/j.issn.1000-6362.2019.04.001

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Based on The Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) FAST-TRACK round’s results, we evaluated rice yield simulations of 6 global gridded crop models (GGCMs) driven by 5 Coupled Model Intercomparison Project Phase 5 (CMIP5) climate datasets from 1980 to 2004 as history period. Subsequently, the multi-crop model ensemble (MCME) was used to predict temporal-spatial distribution of future rice yield over China from the year 2020 to 2099 under different Recommended Concentration Pathways (RCPs). The results showed that MCME provided better performance for historic rice yield distribution with R of 0.798 and RMSE of 1540.6kg·ha^-1 compared to single crop model results. MCME results showed better simulations in the north-east and south-westregions of China, but had poor performance in other regions. Moreover, the MCME overestimated spatial variability. Furthermore, under the increasing of temperature and CO₂ concentration, rice yield had the largest growth of nearly 20% in the late 21st century under RCP8.5 scenario compare to the early 21st century and had a larger growth of 15% under RCP6.0 scenario approximately. For RCP2.6 and RCP4.5 scenarios, rice yield increased in the first half of 21st century, and stayed stable or even slightly decreased in the second half of 21st century, thus leading to a rise of only 4% and 10% respectively by the late 21st century. Rice yield would increase significantly (>40%) in the north-east and south-west regions of China. While other main rice planting areas like middle and lower reaches of Yangtze River and South China only experienced little increase.

The Effects of Nitrogen Deposition on Soil Respiration in an Alpine Meadow in Northern Tibet

GE Yi-qing, YAN Yu-long, LIANG Yan, HASBAGAN Ganjurjav, HU Guo-zheng,YANG Jie, GAO Qing-zhu, HE Shi-cheng, DANJIU Luobu

2019, 40(04):  214-221.  doi:10.3969/j.issn.1000-6362.2019.04.002

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The increase of nitrogen deposition in the world resulted increases of nitrogen input to terrestrial ecosystems and affects soil CO2 emissions. NH₄NO₃ was used to simulated nitrogen deposition to determine the effect of nitrogen deposition on soil respiration during the growing season (June-August) in 2014 in alpine meadow in northern Tibet. The nitrogen deposition rate is 40kgN·ha^-1·y^-1 (N40) according to the distribution pattern of nitrogen deposition in China, the added nitrogen was sprayed onto the N40 plots monthly, while CK plots received the same amount of water. Plant community biomass was measured regularly during the growing season. Meanwhile, the LI-8100 Automated Soil CO₂ Flux System was used to measure soil respiration rates periodically from late June to early September, and measured in two Typical Clear Days as the diurnal dynamics of the soil respiration rate. The main results are showed as follow: (1) nitrogen deposition significantly increased the above-ground biomass in alpine meadow (P<0.05). (2) The soil respiration rate had obvious diurnal and monthly pattern in both treatments. And the diurnal dynamics of soil respiration showed a double peak curve and the peak values were assumed at about 13：00–14：00 and 16：00, respectively. The monthly dynamics of soil respiration showed a single-peak curve, and the maximum appeared in August and lower at early and end of growing season. (3) Nitrogen deposition significantly increased the average soil respiration by 66.1% (P<0.001) compared with control plots in growing season. (4) Soil respiration rates showed a significant positive correlation with soil temperature, soil moisture and above-ground biomass (P<0.001). (5) Nitrogen deposition had no significant effect on temperature sensitivity of soil respiration. The results showed that the increase of soil respiration due to the increase of above-ground and below-ground biomass caused by nitrogen deposition in the alpine meadow.

Phospholipase D of Winter Wheat is Involved in Responses to Drought Stress

WANG Ya-jing, ZHANG Xin-ying, HUANG Gui-rong, FENG Fu, ZHONG Xiu-li

2019, 40(04):  222-229.  doi:10.3969/j.issn.1000-6362.2019.04.003

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Phospholipase D (PLD) mediate signaling processes of various hormones and adversities by hydrolyzing phospholipids in cellular membrane and producing phosphotidic acid (PA), a messenger. In order to investigate the roles and pathways of PLD in regulation of the stability of cellular membrane, PEG-6000 was adopted to mimic drought stress, and n-butabol (BA) was applied to inhibit PLD-derived PA. Drought resistance, stability of cellular membrane, antioxidant enzymes of wheat seedlings treated by PEG and PEG added BA were compared. The results showed that inhibition of PLD by BA induced slower seedling growth, lower net photosynthesis rate, higher non-stomatal limitation, higher membrane ion leakage and malonaldehyde (MDA), a peroxidation product, and lower POD activity. The results indicated that PLD played its role in regulating POD activity. Thus, a potential signal transduction pathway under drought stress mediated by PLD was explored: drought stress—activation of PLD—enhancement of POD—impairation of membrane lipids peroxidation damage—improvement of stability of cellular membrane—increasing drought resistance of plants.

Effect of Elevated CO2 to Starch Metabolizing Enzyme Activities in Grains of Rice

WANG Hui-zhen, WU Rong-sheng, LIN Ru-gang, HAN Xue

2019, 40(04):  230-239.  doi:10.3969/j.issn.1000-6362.2019.04.004

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Free-air CO₂ Enrichment (FACE) experimental system was conducted to find out the change trend of relevant enzymes activity about grain starch synthesis in atmospheric CO₂ concentration, using high yield and good quality japonica varieties Songjing 9 and Daohuaxiang 2. It was treated with two atmospheric CO₂ concentrations: elevated carbon dioxide(600±60μmol·mol^-1) and ambient carbon dioxide(400±40μmol·mol^-1). The ADPG pyrophosphorylase enzyme activity, starch synthase enzyme activity and starch branching enzyme activity in grains of two rice varieties were measured after flowering. The results showed that the effect of elevated CO₂ on the enzyme activity during different grain-filling processes was significantly different, which obviously promoted the expression of ADPG pyrophosphorylase enzyme, soluble and granular starch synthase enzyme activity after the milky stage, but only hindered the expression of starch branching enzyme activity in the grain endosperm at milky stage. Meanwhile, response of starch metabolizing enzyme to elevated CO₂ had the genotypic difference with different rice varieties. For the activity of ADPG pyrophosphorylase enzyme, Songjing9 was more affected by elevated CO₂, while Daohuaxiang2 was more affected by elevated CO₂ for the activity of starch synthase enzyme. The conclusion showed that there was an obvious time characteristics about the influence degree of elevated CO₂ to expression of the key enzyme activity during the starch biosynthetic pathway, with the advancement of grouting process. Response degree of different varieties rice on elevated CO₂ existed significant differences. Overall, atmospheric CO₂ concentration could promote the synthesis of starch in a certain extent.

Characteristics and Forecasting Technology of Greenhouse Temperature Deficit in Southern Plastic Greenhouse

YANG Dong, DING Ye-yi, SUN Jun-bo, LI Qing-bin, WEI Sha-sha, HUANG He-lou

2019, 40(04):  240-249.  doi:10.3969/j.issn.1000-6362.2019.04.005

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The Greenhouse Temperature Deficit (GTD) refers to the phenomenon that the daily minimum temperature in the greenhouse is lower than that outside the greenhouse when insulation measures have been taken. By using the meteorological data and manual operation records (film-covered insulation, window ventilation and so on) of plastic greenhouses in Zhejiang province during the winter and early spring of 2010-2015, the characteristics and key influencing factors of the GTD in southern China were explored. Five common neural networks (BP, GA-BP, RBF, GRNN, PNN) were employed to construct the GTD prediction models. The ensemble forecasting model of the result was built based on the forecasting accuracy of the selected five models. The results showed that: (1) the frequency of GTD in early spring and winter (Mar. and Dec.) was three times higher than that in severe winter (Jan.-Feb). The occurrence probability of the GTD at 1.5m was three times higher than that at 0.5m. At the height of 0.5m, the probability of GTD at the edge was 8 to 13 times higher than that at the center. At the height of 1.5m, the difference in the probability of GTD between the center and edge was small. (2) When the GTD happened, the daily minimum temperature outside the greenhouse mainly concentrated on 2 to 11 degrees Celsius, and the insulation method was single film or double film coverage, the proportion of single film coverage was over 93%. The GTD mostly occurred when the opening height of the east and west side windows was high (35?40cm) in daytime and the small gap ventilation was put in the night. When the GTD occurred at 0.5m, the weather conditions were obviously deviated from that of 1.5m. The daily minimum relative humidity, total cloud and average daily wind speed were higher, and the sunshine hours were less. (3) The prediction accuracy of the five selected neural networks for the GTD was basically about 80%, and the GA-BP model was with the highest prediction accuracy. The ensemble model for GTD at 0.5m height was above 85%, and that at 1.5m height was above 80%. The stability of ensemble model was better than that of single model.

Effect of Spatial Scale of DEM on Spatial Simulation of Duration of Possible Sunshine: A Case Study in Xianju County, Zhejiang Province

LI Jun，WANG Chao，ZHAO Yu-zhu

2019, 40(04):  250-259.  doi:10.3969/j.issn.1000-6362.2019.04.006

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To analyze the effects of DEM with different spatial resolution on the numerical simulation of Duration of Possible Sunshine (DPS) based on DEM, Xianju County in Zhejiang Province was selected as the study area. DEM data with four spatial resolutions (10m, 30m, 90m, and 900m) derived from 1:10000 digital topographic map, ASTER GDEM, SRTM and GTOPO30′, respectively were used in this study. The topographic factors of altitude, slope, aspect, etc were derived from DEM. Using digital terrain analysis and spatial analysis for topographic factors and the distributed statistical model of DPS in GIS platform, this paper simulated the spatial distribution of DPS with four spatial resolutions in January and July. Then the effect of DEM scale on DPS simulation was analyzed. The results showed that spatial heterogeneity of DPS decreased as the spatial resolution decreased. Spatial distribution characteristics of DPS with topographic factors became increasingly hard to identify. The spatial data statistics showed that the average value increased with decreasing spatial resolution, while the standard deviation decreased. The maximum value varied little with spatial resolution, but the minimum value was quite different. Affected by altitude and other topographical factors, DPS was longest on flat and mountain ridges, while it was shortest in the region distributed at altitudes from 200?400m above sea-level. Moreover, it increased with the increasing altitude from 400-1100m above sea-level. Taking the DPS with 10m resolution as reference, the difference between the DPS with the other three spatial resolutions and the DPS with 10m resolution increased with the decrease of resolution. The minimum was at an altitude of <100m. The greatest differences were concentrated in the region of 700-900m. The average daily DPS in January were about 0.7h, 1.4h, and 2.9h more, while the one in July were about 0.5h, 0.9h, and 2.3h more. The DPS decreased with the increase of slope when the slope was in the range of 0-55°. The difference between the DPS with three spatial resolutions (30m, 90m, and 900m) and the reference value with 10m resolution increased with the decrease of resolution. The minimum all appeared in the flat region of slope 0-5°. The maximum occurred in the area with a steeper slope. The average daily DPS in January were about 2.1h, 1.8h, and 1.7h more, while the one in July were about 0.3h, 0.6h, and 1.2h more. Due to the effect of sloar altitude and azimuth angle, there was a great DPS differences between the south slope and the north slope. While the differences between SE slope and SW slope, E slope and W slope, NE slope and NW slope were smaller. The DPS differences with the reference value in all slopes increased with the decrease of resolution. In the northern slope (N, NE, and NW slopes), the difference in January was greater than that in July. The maximum occurred in the northern (N slope) slope of January. The average daily DPS were about 1.4h, 2.5h, and 4.8h more. In the southern slope (S, SE, and SW slopes), the difference in January was less than that in July. The maximum occurred in the southern slope (S or SW slope) of July. The average daily DPS were about 0.5h, 0.9h, and 2.1h more.

Micrometeorological Analysis of the Effects of Different Irrigation Water Sources on the Heat Stress of Rice

JIANG Xiao-dong, HUA Meng-fei, HU Ning, SHEN Shuang-he, YANG Xiao-ya, YANG Shen-bin, GUO Jian-mao

2019, 40(04):  260-268.  doi:10.3969/j.issn.1000-6362.2019.04.007

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Heat stress is one of the common agrometeorological disasters in the rice production in the middle and lower reaches of the Yangtze River in China. To mitigate the effect of heat stress on rice growth, irrigation with pond or well water was usually adopted, and which is considered to be an effective measure. In this paper, the effect of the irrigation with different water sources was evaluated by a field experiment conducted in Nanjing from August 12th to 18th, 2016, during which time a heat stress had just occurred. The rice variety Liangyoupeijiu was used in the experiment and three daily irrigation treatments, set as T1, T2 and CK, were implemented. For T1 and CK, pond water was used for the irrigation, and well water was used for T2. For all treatments, the irrigation started from 8：00 and stopped when the height of water layer reached about 10 cm. For T1 and T2, the paddy water was drained out at 18：00; but for CK, the water was kept with a height between 5 and 10cm. The average temperature was about 30.5℃ and 18.2℃ for pond and well water respectively. Since CK kept the water in the field, the average temperature of the paddy field water at 8：00 was about 28.2℃. The temperature and humidity within the rice canopy at four different heights (40cm, 80cm, 120cm and 130 cm), leaf temperature at the canopy top, and solar radiation above the canopy were measured. With the observations, the diurnal variation of each energy balance component in the paddy field was calculated using the Penman-Monteith stratification model. The micrometeorological characteristics of the paddy fields were analyzed. The results showed that from 8：00 to 18：00, the order of canopy temperatures for three treatments were T1>CK>T2. However, the difference of the canopy temperatures among the treatments decreased with the height within the canopy. Similarly, the difference of paddy soil temperatures among the treatments decreased with the depth in the soil. From 18：00 to 8：00, the difference of soil temperature at 5cm depth was the most obvious among the treatments. The difference of the canopy temperature at 40cm height within the canopy was the second one. The analysis indicated that the relationship between the changes of the energy balance of paddy fields and the irrigation water was close. The order of the heat storage in water (Q) was T2 >CK >T1. And the orders of soil heat flux (G), sensible heat flux (H) and latent heat flux (LE) were T1>CK >T2. These results suggested that irrigation with pond water could aggravate the heat stress on rice, while irrigation with well water is benefit to reduce the effect of heat stress on rice growth.